Woven tubular gaskets have been used for the principal purpose of oven door seals for many years. These gaskets are typically made from a combination of an inner tubular support member formed of knitted wire and an outer tubular member made either by braiding, knitting or weaving from an insulating material such as glass fiber yarn. Such structures have proven to be durable at the high temperatures used in self-cleaning ovens and provide a good seal despite repeated openings and closures of the oven door over many years of use. An inner tubular member, sometimes called a bulb, provides the necessary resilient support of the glass fiber tubular gasket. Various methods of attaching the knitted wire tubular gasket to ovens or oven doors have typically comprised providing a retaining member which extends along the gasket and locking the retaining member between sheet metal pieces of the oven door or by providing clamps at spaced locations around the periphery of the gasket. Examples of such oven gaskets and their attachment are shown in U.S. Pat. No. 2,219,962 to Reynolds et al; U.S. Pat. No. 3,578,764 to Nunnally et al; U.S. Pat. No. 3,812,316 to Milburn; U.S. Pat. No. 3,846,608 to Valles; and U.S. Pat. No. 4,122,323 to Stats.
An alternative form of gasket having attachment means comprised of a wireform having spaced attachment protrusions which fit into corresponding apertures in a surface to which the gasket is to be attached is shown in U.S. Pat. Nos. 4,822,060 and 5,395,126. In the '126 patent, the interior support core is eliminated. Wire interbraided with glass fiber forms a support matrix which also locks the protrusions in place.
Although gaskets of the above patents are effective for their intended purpose, fabrication requires a relatively high level of skill which makes the product relatively expensive. A problem may arise in the production of gaskets of the '060 patent owing to the difficulty of insertion of the wireform carrying the protrusions through the knitted tubular wire bulb and then in the passage of the protrusions through the bulb and the overlayer of braided gasket material. Not only does the insertion of the wireform tend to be a difficult task to accomplish, the passage of the protrusions through the exterior gasket layer may tear the individual strands of glass fiber if not carefully done, resulting in a potentially undesirable scrap rate. Further, because the surfaces to which the gaskets are to be attached have attachment apertures preformed at different spacings for different products, a range of wireforms having different spacings for the attachment protrusions must be provided.
Still another form of attachment means comprises individual clips as disclosed, for example, in U.S. Pat. Nos. 4,986,033, 5,107,623 and 5,205,075. The '075 patent discloses a clip having an apex and pointed ends which are bent laterally so as to project between an interknitted bulb and an outer gasket layer. The interknitted bulb is effective to maintain the clips in an upright position so that the pointed ends extend outwardly from the gasket in a radial direction in order to facilitate insertion into the apertures formed in one of the oven surfaces.
Clips of the type shown in the '075 patent are inserted from the interior of the gasket and passed through the exterior gasket wall and may be inserted at variable spacing along the gasket. However, radial expansion and contraction of the braid with corresponding axial contractions and expansions is not suggested in conjunction with variable aperture or clip spacing as a means of providing a gasket of varying diameter.